In 2002, it was estimated that there were 10.9 million new cases of cancer and 6.7 million cancer-related deaths worldwide. Globally, prostate cancer has become the third most common cancer in men, with half a million new cases each year, amounting to about 10% of all male cancers. It is the most common cancer after skin cancer, and is the second leading cause of cancer-related death in men in the United States. Breast cancer is the most frequent cancer of women, accounting for 23% of all cancers. Liver cancer is the fifth most common cancer in the world, and most of the liver cancer cases occur in developing countries, especially the Far East and Southeast Asia. The prevalence of liver cancer in developing countries and the emergence of prostate cancer and breast cancer as public health problems in developed countries have put tremendous pressure on the healthcare systems to provide new and effective treatments.
Current understanding of cancer cell biology has allowed scientists to develop a rational approach to combat cancer cells by using a combination of anti-cancer drugs, which would inactivate and/or activate, respectively, multiple targets in cell growth-promoting and growth-inhibitory signaling pathways. Clearly, there is an unmet clinical need to develop novel therapeutic agents which can act effectively alone and/or in combination with conventional radiation or chemotherapy to halt or reverse the progression of advanced cancer. Such demand has fueled the search for novel endo-/para-/autocrine growth-promoting and growth-inhibitory signaling pathways important in cancer pathogenesis, which may yield new therapeutic agents or targets for anti-cancer drug discovery and development.
PDZ domain-containing protein 2 (PDZD2) (also named KIAA0300, PIN-1, PAPIN, activated in prostate cancer (AIPC), and PDZ domain-containing protein 3 (PDZK3)), is a six-PDZ (for PSD95, Discs-large, and ZO-1) domain protein which is expressed in multiple tissues. Though proteins containing PDZ domains have been shown to bind specific C-terminal protein sequences of transmembrane receptors or ion channels, and are believed to be involved in mediating intracellular protein-protein interactions, protein scaffolding and intracellular signaling, the functions of PDZD2 in humans are as yet little understood.